Hot-air furnace.



No. 708,563. Patented Sept. 9, I902. T .1. r. KRAUTER. I

HOT AIR FURNACE. A umion filed Feb. 14, 1901.

(No Model.)

2 Sheets-Sheat l.

.1. F. KRAUTEB.

HUT AIR FURNACE.

(Application flled Feb. 14, 1901.

(No Model.) 2 Sheets-Shut 2.

WW ii/wvmwbovq ma NORRIS PEYERS ca. FNOTQLXTHQ, WASHINGTON, n. c.

JOHN FREDERICK KRAUTER, OF TOLEDO, OHIO.

HOT-AIR FURNACE.

SPECIFICATION forming part of LettersPatent No. 708,563, dated September 9, 1902.

Application filed February 1Q, 1901. Serial No, 47,205. (No model.)

T0 at whom it may concern.-

Be it known that I, JOHN FREDERICK KRAUTER, a citizen of the United States, residing at Toledo, in the county of Lucas and State of Ohio, have invented a new and useful Improvement in Hot-Air Furnaces, of which the following is a specification.

My invention relates to improvements in hot-air furnaces, and has for its object to provide a furnace of the kind that is efficient and economical; furthermore, that may be adapted to burn either hard or soft coal with a minimum loss of fuel and heat from im' perfect combustion and radiation. I attain these objects by providing a furnace having a high degree of efficiency as to combustion, with a radiator adapted to transmit an increased percentage of the heat produced in the furnace to a passing volume of air. The construction by which these results are attained is hereinafter described, and illus trated in the drawings.

I have found in practice that air by reason of its non-conducting properties is slow to receive heat and when heated is equally slow to give it off, that. in order to radiate the greatest amount of heat from a volume of heated air or gases it is necessary to pass it thinly over or between good conductingplates, and that to heat a volume of air it is best accomplished by passing it thinly over or between heated conducting-plates. I have also found that when the same volume of heated air is passed through cylindrical or cubical shaped flues or passages a large proportion of the heat is lost. In the construction'of my improved furnace I have therefore provided circuitous narrow passages for the heated air and gases from the furnace to the flue between broad plates, which also form the sides of narrow intervening air-fl ues connecting the air-chamber in the bottom with the air-chamber in the top of the outer casing of the furnace.

In the drawings, Figure 1 is a transverse vertical section through a fu rnace constructed according to my invention. Fig. 2 is a horizontal section on the line cox of Fig. 1. Fig. 3 is an enlarged detail view of the annular air-chamber formed by the perforated sectional lining and the top section of the firepot. Fig. at is a top plan View of the top posed and supported by the fire-pot.

plate of the heating-drum, showing the airpassages. Fig; 5 is a top plan view of the top section of the fire-pot. Fig. 6 is a modification of same as adapted for a hard-coal furnace. Fig. 7 is a part elevation and part section of the fuel-door and fuel-door opening, and Fig. 8 is a horizontal section show ing a modified form of a heating-drum.

In the drawings, A designates the ash-pan, which is of the usual form of construction and is provided with the necessary fittings, such as grates and doors. Upon this ash-pan is mounted the sectional fire-pot, composed of bottom section 1, intermediate section 2, and top section B, which latter is flared outward toward the top and has formed upon its rim a rabbet 3, and near the base of the section there is formed an inner shoulder 4.

G designates the heating-drum,superim- The drum comprises a fire-pot dome 5 and intermediate semicircular heating-drum 6 and an outer heating-drum 7. The intermediate heating-drum communicates with the dome over the fire-pot at the rear of the furnace through the ilue 8, which extends from the bottom to the top. From this flue-opening the drum curves concentrically upon both sides of the dome toward the fuel-opening 9 of the furnace. Opposite the fuel-duct the ends of the innerheating-drum are reversely curved outward to form return-elbows 10, which communicate with the outer heatingdrum 7, which in a like manner concentrically encircles the inner heating-drum. The course of the gases during the operation of the furnace is indicated in Fig. 2, and, as will be seen by the direction of arrows, the gases will pass from the dome through the flue 8 into the intermediate heating-drum and circle toward the front upon both sides of the dome and return through the outer drum 7,from which the gases find exit through the smoke-pipe collar 11. By thus providing an inner and an outer heating-drum arranged concentrically around the dome over the firepot I have greatly increased the heating-surface of a furnace by forming the annular air ducts 12 between the dome and the intermediate heating-drum. and the annular airducts 13 between the drums 6 and 7, and upon inclosing the heater in the furnace-casing 14 the usual air-duct is formed. For starting a fire in the furnace a direct draft is desired, which is-provided for by a flue-collar 16 between theinner and outer heating-drums in a line with the flue'8 and the smoke-pipe collar 11. In the collar 16 there is mounted a damper 17, by means of which the gases of combustion may be allowed to escape directly into the smoke-pipe or by closing of the damper the gases are obliged to travel through the inner drum toward the front of the furnace and then through the outer drum to the smoke-pipe. The drums and dome are constructed of sheet metal and are clamped between and closed by the bottom plate 18 and the top plate 19 in the usual manner. Both of the plates 18 and 19 are provided with openings for the passage of air between the dome and the drums and between the drums, and to the bottom plate and the dome there is suitably bolted the fuel-supplyduct 9, communicating with the interior of the dome. In the side walls 20 of the duct 9 there are formed openings 21, normally covered by removable sliding plates 22. By removing the plates access may behad through these openings to both drums for the purpose of cleaning through the connecting-throats 23.

24 designates clean out doors, through which the rear portion of the outer drum may be reached for cleaning.

25 designates a flange integral with the bottom plate 18 and encircling the dome-opening of the plate, and in diameter is adapted to enter the rabbet 3 of section B of the firepot. Uponthe top of the plate around the same opening there is also formed a rabbet 26 of a depth to receive the flange 27 of the lining D. The lining D is made of sections 28, which are suitably perforated and provided with incuts 29 upon their bottom edges, which are supported upon the shoulder 4. When the sections of the lining are assembled in position within the fire-pot, an annular air-space 30 is formed to supply air to the fire above the fuel through the incuts and perforations in the lining. The air in the chamber is replenished through a duct 31, which is secured to the under side of the fuelduct, and the draft of air is controlled by means ofa sliding valve 32, by means of which the openings 33in the fnel-doorframe 34 may be closed. The fire-pot section B is dished and provided with a projecting lip 34: of depth and width to receive the air-duct 31. For a hard-coal furnace the duct 31 is omitted and a fire-pot section 35 substituted without the sectional lining to form an air chamber. Otherwise no alterations are made in construction of the furnace to use hard coal.

In the modification shown in Fig. 8 I have provided a single heating-drum 36, provided with an internal diaphragm 37, to cause a like flow of the gases as in the furnace arranged with a double drum. A direct-draft damper 38 is mounted on the collar 39, which is secured to the diaphragm in a line with the flue-opening 8 and the smoke-pipe collar 11. This form of radiator, while it embodies the principle of construction of my invention, is not as desirable as that shown in the other figures, because of the reduced radiating-surface.

As appears in the drawings, the heatingdrums are upon the same level as the dome over the fire-pot, and with it constitute a compact radiator provided with largely-increased heating-surface surrounding contracted air-passages, formed to draw air in thin volumes between the highly -heated plates of the dome and drums from the airsupply in the base to the distributing-chamher in the top of the casing. By this construction a largely-increased percentage of the heat generated in the furnace is utilized, thereby lessening the quantity of fuel required. In furnaces heretofore constructed little air can come in contact with the dome of the fire-pot over the fuel-supply duct, thereby reducing their efficiency, which defeet is also remedied by my construction.

What I claim to be new, and desire to secure by Letters Patent, is-

1. In a hot-air furnace, the combination with a fire-pot, of a radiator comprising a central cylindrical dome mounted on the firepot and having a fuel-duct for the fire-pot extending from one side and a flue opening opposite therefrom into an inner drum extending concentrically around the dome to opposite sides of the fuel-duct; an outer drum concentrically disposed around the inner drum and connected at opposite sides'of the fuel-duct by elbows with the inner drum; narrow vertical airpassages between the outer and inner drums and between the inner drum and the dome; an exit-flue for the outer drum set horizontally opposite the flue of the dome, and an intermediate flue connecting the outer and inner drums in alinement with the exit-flue and having a damper adapted, when open, to admit direct draft from the flue of the dome through the intermediate flue to the exit-flue, and, when closed, to force the d raftcircuitously through the drums.

2. In a hot-air furnace, the combination with a fire-pot having an outwardly-flared detachable top section provided with an inner shoulder around the base of the section, and with an incut at one side in its rim, of an annular base-plate for the dome mounted horizontally on the fire-pot, with its inner rim on the rim of the top section, a dome for the fire-pot, provided with a side opening and mounted on the base-plate concentric with its inner rim, a perforated lining for the top section of the fire-pot, formed of detachable sections, having the lower ends of the sections supported on the inner shoulder of the top section, and the upper ends curved outward and supported by the inner rim of the horizontal plate, forming, with the top section of the fire-pot and the rim of the plate, an annular air-space around and within the top of the firepot, plates secured to the annular horizontal plate, and to the dome around its side opening, forming a fuel-duct for the fire-pot, a plate angled at the sides and secured to the base-plate beneath the fuel-duct, and to the top section of the firepot around the opening formed by the side incut in its riin, forming an air-duct for the 

